Many illusion items include an illusion buff. Many of these buffs don't seem to make sense in their description. Example, it may often say, "Increases your by Armor 5 to 0." May of these items have the same / similar wording. Does this mean at higher levels the buff is is Zero, but 5 at lower levels? Or is this simply backwards and the buff is a max of 5 Armor, at higher levels? Or something else entirely?
It means the display of the data being pulled is just plain messed up. https://www.raidloot.com/Spells.aspx?name=illusion benefit
They had done some code work before to help them with the descriptions and some things got moved around. For anything displaying a wonky description, post in the bug report form the name of the item, the name of the buff, and whether it is the item description that is off or the spell description on the buff icon. There have been a number of ones they have had to go back and fix.